Operation Deep Scope 2005: Mission Plan

Operation
Deep Scope 2004 looked into the deep ocean with new eyes and
revealed new organisms, behaviors, visual adaptations, and fluorescent
compounds. Notable
results from this mission included the discovery of a fluorescent shark,
the fluorescence of methane hydrates, the first in situ footage
of a large, undescribed species of deep-sea squid, the discovery of
a bioluminescent anemone, the discovery that animals that appear to be
transparent in the open ocean are clearly visible under polarized light,
and the discovery that organisms collected under bright submersible lights
are irreparably blinded. On Operation Deep
Scope 2005, we will
extend the envelope of this exciting frontier in ocean exploration with
even more methods of seeing and collecting. Our target field sites
will be some deep Lophelia lithoherms
on the southwest Florida shelf, Viosca Knoll and the unexplored pinnacles on
the west margin of DeSoto Canyon in the northern Gulf of Mexico. Read more
on the dive sites in the Geology essay.

Characterizing deep-sea habitats

Characterizing deep-sea benthic (bottom) and pelagic (water column) ecosystems
has proven to be a great challenge in the deep-sea environment, as many
of the large predators flee from noisy, brightly lit submersibles and ROVs.
In addition to the temporary disruption of normal behavior, animals with
photoreceptors designed for the dimly lit deep-sea environment are often
permanently blinded by the very lights we use to find them. Our
assumption that everything sees the way we see has also affected descriptions
of animal interactions, in that animals that may be transparent, and therefore
virtually invisible to humans under bright submersible lights, are much
more visible to animals with polarization and/or UV sensitivity.

Deep Scope 2004 brought together an international
team of investigators, all interested in various aspects of light and how
it affects animal interactions. Due to the multidisciplinary nature
of the research, numerous scientists were able to collect data on each
submersible dive, resulting in a wealth of data rarely seen on such a short
mission. Operation Deep Scope 2005 seeks
to build on results of 2004, continuing our studies with proven technologies,
as well as using new technologies. During the Deep-Scope 2005 mission,
our objectives are to:

1) Continue unobtrusive observations

During Deep Scope 2004, a unique deep-sea observatory
called Eye-in-the-Sea (EITS) was deployed by the Johnson-Sea-Link (JSL)
submersible at three different locations on the sea floor. This battery
powered camera system uses a red-light emitting diodein combination with
a low-light level camera. Data recorded by EITS during this initial
deployment included the first ever in situ footage of a large
(> 2 m length), previously undescribed species of deep-sea squid (M.
Vecchione pers. comm.). However, during deployments over the last
two years, it became clear that some fish were responding to red light
illumination. For Deep Scope 2005, the lighting system on EITS will
be modified to incorporate some high intensity far-red LEDs used together
with a long pass filter to filter out any shorter wavelengths that these
animals might be responding to.

In addition to making observations under the new illumination system,
behavioral responses to a variety of artificial bioluminescent lures will
be tested, in hopes of getting more information on the role of bioluminescence
in the deep-sea environment

Visual displays are one of the most important means of communication between
organisms, at both within- and between-species levels. In the shallow oceanic
environment (0-10 m), the spectrum of the ambient light is broad enough
for pigments to generate color displays, such as in coral reef fishes.
Deep in the ocean, where there is very little ambient light (below 700-1000
m), bioluminescence is the only way to send a visual signal. At intermediate
depths (100 - 300 m), which are still relatively well lit during daytime,
neither of these mechanisms function efficiently. There is too much light
for a bioluminescent flash to stand out against the background, while color
displays based on pigments are impossible since the downwelling light does
not contain enough spectral diversity – everything appears in various
shades of blue. The only way to generate a color other than blue under
such circumstances is to use a fluorescent compound (fluorochrome), which
absorbs blue light and emits light of another (longer wavelength) color
(green, yellow, orange or red). Therefore, fluorescence may be a major
mechanism of visual communication between organisms at intermediate depths.

During Deep Scope 2004, fluorescence imagery was used to detect
camouflaged animals that were otherwise difficult to see. Under fluorescence
imagery, benthic animals that were virtually invisible under white light
became very visible. We plan to continue to search on this mission
for deep-sea organisms in which fluorescence is likely to be functional.
We hope to obtain a more complete picture of deep-sea benthic fluorescence
and develop ideas about its possible functions from the spectral characteristics
and patterns observed in the animals. In particular, we would like to assess
the possibility that the fluorescence of some animals may be stimulated
by bioluminescence produced by other organisms. This understanding
of fluorescence responses is being investigated as a tool for automated
spectral image classification of bottom habitats (Mazel et al. 2003).

3) Quantify the deep-sea light environment as it is perceived
by its inhabitants

The Operation Deep Scope 2004 cruise greatly
increased our knowledge of camouflage in the ocean. Two of the most
notable results were that: 1) the colors of both benthic and pelagic animals
are very well matched for camouflage, and 2) the ultimate camouflage, invisibility,
can be broken by animals with the ability to see polarized light. On
Deep-Scope 2005, we plan to extend these studies, looking at UV vision
as a way of detecting transparent animals. We’re going to examine
the sensory world of UV-visual species by filming transparent animals underwater
using specialized UV cameras and by measuring the underwater UV levels
using spectroradiometers. We also plan to film and photograph transparent
animals at UV wavelengths. In addition, we will be measuring
the levels of UV light in situ, and comparing these results with
measurements of UV visual sensitivity in animals collected from near-surface
waters.

In order to examine the deep-sea environment from the perspective of the
animals living there, we’re going to modify the lights and cameras
on the sub to function as “animal eyes”. Almost all deep-sea
visual systems studied to date are sensitive to only blue-green light,
and that also happens to be the color of the remaining background light
in the deep-sea. Therefore, full color imaging of animals illuminated
by full-spectrum lighting gives us a very poor understanding of the deep-sea
world as seen by its inhabitants. Many animals that appear conspicuous
to us are in fact well camouflaged. Certain body patterns visible
to us may not be visible at depth. In order the see the deep-sea
environment the way a deep-sea animal would, lights of the Johnson-Sea-Link submersible
will be covered with filters that, together with the spectral emission
of the lights and the spectral response of the video camera, mimic the
response of the typical deep-sea visual system under the ambient light
found at 300 m depth.

4) Examine the role of polarized light reception

Many near-surface animals can see polarized light. As demonstrated
on Deep Scope 2004, the ability to see polarized
light greatly increases the ability to see transparent animals in the pelagic
zone. Using the new technology of polarizing videography, we measured
polarized light and observed pelagic zooplankton in the lab, during surface
operations (blue water dives) and during submersible dives. We
confirmed that many of the transparent animals found in the open ocean
are highly visible when viewed using polarized filters (see Polarization
Vision essay for images). This is a form of camouflage breaking that
could be used by animals with polarization vision. On Deep
Scope 2005, we will be extending these studies to determine
the range at which polarization sensitivity can enhance contrast. This
will be examined by setting up a contrast target in the blue-water environment,
and imaging it using polarizing videography over a range of distances. Selected
frames will be digitized and then analyzed in several ways.

Polarization vision in deep-sea animals will be tested electrophysiologically,
and examined structurally on animals captured without exposure to light.
Read more in the Animal Capture essay.

5) Examine of the visual physiology/optics of deep-benthic
invertebrates

In spite of the very dim light below 700 m, many species inhabiting the
benthos below this depth possess very large eyes. In deep-living
pelagic species, it’s been shown that bioluminescence had a significant
impact on photoreceptor size and function (Douglas et al. 1998). The
question arises as to whether bioluminescence might be the driving force
behind the large photoreceptors of benthic species. This will
be examined using microspectrophotometry and electrophysiology on crustaceans
obtained using new collection techniques described under Capturing Animals.
Eyes of deep-sea species are also very likely adapted for the detection
of point sources of bioluminescence. Structural modifications that increase
sensitivity to the available light, such as an increase in rhabdom width/length,
reflecting and refracting cone optics, increase in interommatidial angle,
and/or presence of a reflecting tapeta, will be examined histologically,
using both light and transmission electron microscopy. This
work has the potential to provide new methods for increasing the sensitivity
of artificial detectors.

6) Determine of whether deep-sea benthic species being blinded
by science

There has been recent concern that repeated visits to deep-sea benthic sites
with brightly lit submersibles and ROVs may be causing irreparable damage
to the very large, presumably very sensitive, photoreceptors of some of the
major motile predators in these ecosystems (Gaten et al, 1998; Herring et
al. 1999). On this mission, we hope to obtain, for the first time,
deep-sea benthic crustaceans intact photoreceptors. These eyes will
be studied electrophysiologically to determine how sensitive they are to
light. In addition, some of the animals will be exposed to lights that
are identical in intensity and duration to what they might experience when
hit by the lights of a submersible or ROV, and their sensitivity will be
compared to that of unexposed animals. Some of the animals that will
be exposed to light will be allowed to recover in the dark for various periods
of time, to determine if they can recover from this intensity of light exposure,
or are permanently blinded.